Hi, everybody!
Tor 0.2.9.1-alpha is the first alpha release in the 0.2.9 development
series. It improves our support for hardened builds and compiler
warnings, deploys some critical infrastructure for improvements to
hidden services, includes a new timing backend that we hope to use for
better support for traffic padding, makes it easier for programmers to
log unexpected events, and contains other small improvements to
security, correctness, and performance.
You can download the source from the usual place on the website.
Packages should be available over the next several days. Remember
to check the signatures!
Please note: This is an alpha release. You should only try this one if
you are interested in tracking Tor development, testing new features,
making sure that Tor still builds on unusual platforms, or generally
trying to hunt down bugs.
Below are the changes since 0.2.8.6.
Changes in version 0.2.9.1-alpha - 2016-08-08
o New system requirements:
- Tor now requires Libevent version 2.0.10-stable or later. Older
versions of Libevent have less efficient backends for several
platforms, and lack the DNS code that we use for our server-side
DNS support. This implements ticket 19554.
- Tor now requires zlib version 1.2 or later, for security,
efficiency, and (eventually) gzip support. (Back when we started,
zlib 1.1 and zlib 1.0 were still found in the wild. 1.2 was
released in 2003. We recommend the latest version.)
o Major features (build, hardening):
- Tor now builds with -ftrapv by default on compilers that support
it. This option detects signed integer overflow (which C forbids),
and turns it into a hard-failure. We do not apply this option to
code that needs to run in constant time to avoid side-channels;
instead, we use -fwrapv in that code. Closes ticket 17983.
- When --enable-expensive-hardening is selected, stop applying the
clang/gcc sanitizers to code that needs to run in constant time.
Although we are aware of no introduced side-channels, we are not
able to prove that there are none. Related to ticket 17983.
o Major features (compilation):
- Our big list of extra GCC warnings is now enabled by default when
building with GCC (or with anything like Clang that claims to be
GCC-compatible). To make all warnings into fatal compilation
errors, pass --enable-fatal-warnings to configure. Closes
ticket 19044.
- Use the Autoconf macro AC_USE_SYSTEM_EXTENSIONS to automatically
turn on C and POSIX extensions. (Previously, we attempted to do
this on an ad hoc basis.) Closes ticket 19139.
o Major features (directory authorities, hidden services):
- Directory authorities can now perform the shared randomness
protocol specified by proposal 250. Using this protocol, directory
authorities generate a global fresh random value every day. In the
future, this value will be used by hidden services to select
HSDirs. This release implements the directory authority feature;
the hidden service side will be implemented in the future as part
of proposal 224. Resolves ticket 16943; implements proposal 250.
o Major features (downloading, random exponential backoff):
- When we fail to download an object from a directory service, wait
for an (exponentially increasing) randomized amount of time before
retrying, rather than a fixed interval as we did before. This
prevents a group of Tor instances from becoming too synchronized,
or a single Tor instance from becoming too predictable, in its
download schedule. Closes ticket 15942.
o Major bugfixes (exit policies):
- Avoid disclosing exit outbound bind addresses, configured port
bind addresses, and local interface addresses in relay descriptors
by default under ExitPolicyRejectPrivate. Instead, only reject
these (otherwise unlisted) addresses if
ExitPolicyRejectLocalInterfaces is set. Fixes bug 18456; bugfix on
0.2.7.2-alpha. Patch by teor.
o Major bugfixes (hidden service client):
- Allow Tor clients with appropriate controllers to work with
FetchHidServDescriptors set to 0. Previously, this option also
disabled descriptor cache lookup, thus breaking hidden services
entirely. Fixes bug 18704; bugfix on 0.2.0.20-rc. Patch by "twim".
o Minor features (build, hardening):
- Detect and work around a libclang_rt problem that would prevent
clang from finding __mulodi4() on some 32-bit platforms, and thus
keep -ftrapv from linking on those systems. Closes ticket 19079.
- When building on a system without runtime support for the runtime
hardening options, try to log a useful warning at configuration
time, rather than an incomprehensible warning at link time. If
expensive hardening was requested, this warning becomes an error.
Closes ticket 18895.
o Minor features (code safety):
- In our integer-parsing functions, ensure that maxiumum value we
give is no smaller than the minimum value. Closes ticket 19063;
patch from U+039b.
o Minor features (controller):
- Implement new GETINFO queries for all downloads that use
download_status_t to schedule retries. This allows controllers to
examine the schedule for pending downloads. Closes ticket 19323.
- Allow controllers to configure basic client authorization on
hidden services when they create them with the ADD_ONION control
command. Implements ticket 15588. Patch by "special".
- Fire a STATUS_SERVER controller event whenever the hibernation
status changes between "awake"/"soft"/"hard". Closes ticket 18685.
o Minor features (directory authority):
- Directory authorities now only give the Guard flag to a relay if
they are also giving it the Stable flag. This change allows us to
simplify path selection for clients. It should have minimal effect
in practice, since >99% of Guards already have the Stable flag.
Implements ticket 18624.
- Directory authorities now write their v3-status-votes file out to
disk earlier in the consensus process, so we have a record of the
votes even if we abort the consensus process. Resolves
ticket 19036.
o Minor features (hidden service):
- Stop being so strict about the payload length of "rendezvous1"
cells. We used to be locked in to the "TAP" handshake length, and
now we can handle better handshakes like "ntor". Resolves
ticket 18998.
o Minor features (infrastructure, time):
- Tor now uses the operating system's monotonic timers (where
available) for internal fine-grained timing. Previously we would
look at the system clock, and then attempt to compensate for the
clock running backwards. Closes ticket 18908.
- Tor now includes an improved timer backend, so that we can
efficiently support tens or hundreds of thousands of concurrent
timers, as will be needed for some of our planned anti-traffic-
analysis work. This code is based on William Ahern's "timeout.c"
project, which implements a "tickless hierarchical timing wheel".
Closes ticket 18365.
o Minor features (logging):
- Provide a more useful warning message when configured with an
invalid Nickname. Closes ticket 18300; patch from "icanhasaccount".
- When dumping unparseable router descriptors, optionally store them
in separate files, named by digest, up to a configurable size
limit. You can change the size limit by setting the
MaxUnparseableDescSizeToLog option, and disable this feature by
setting that option to 0. Closes ticket 18322.
- Add a set of macros to check nonfatal assertions, for internal
use. Migrating more of our checks to these should help us avoid
needless crash bugs. Closes ticket 18613.
o Minor features (performance):
- Changer the "optimistic data" extension from "off by default" to
"on by default". The default was ordinarily overridden by a
consensus option, but when clients were bootstrapping for the
first time, they would not have a consensus to get the option
from. Changing this default When fetching a consensus for the
first time, use optimistic data. This saves a round-trip during
startup. Closes ticket 18815.
o Minor features (relay, usability):
- When the directory authorities refuse a bad relay's descriptor,
encourage the relay operator to contact us. Many relay operators
won't notice this line in their logs, but it's a win if even a few
learn why we don't like what their relay was doing. Resolves
ticket 18760.
o Minor features (testing):
- Let backtrace tests work correctly under AddressSanitizer. Fixes
part of bug 18934; bugfix on 0.2.5.2-alpha.
- Move the test-network.sh script to chutney, and modify tor's test-
network.sh to call the (newer) chutney version when available.
Resolves ticket 19116. Patch by teor.
- Use the lcov convention for marking lines as unreachable, so that
we don't count them when we're generating test coverage data.
Update our coverage tools to understand this convention. Closes
ticket 16792.
o Minor bugfixes (bootstrap):
- Remember the directory we fetched the consensus or previous
certificates from, and use it to fetch future authority
certificates. This change improves bootstrapping performance.
Fixes bug 18963; bugfix on 0.2.8.1-alpha.
o Minor bugfixes (build):
- The test-stem and test-network makefile targets now depend only on
the tor binary that they are testing. Previously, they depended on
"make all". Fixes bug 18240; bugfix on 0.2.8.2-alpha. Based on a
patch from "cypherpunks".
o Minor bugfixes (circuits):
- Make sure extend_info_from_router() is only called on servers.
Fixes bug 19639; bugfix on 0.2.8.1-alpha.
o Minor bugfixes (compilation):
- When building with Clang, use a full set of GCC warnings.
(Previously, we included only a subset, because of the way we
detected them.) Fixes bug 19216; bugfix on 0.2.0.1-alpha.
o Minor bugfixes (directory authority):
- Authorities now sort the "package" lines in their votes, for ease
of debugging. (They are already sorted in consensus documents.)
Fixes bug 18840; bugfix on 0.2.6.3-alpha.
- When parsing a detached signature, make sure we use the length of
the digest algorithm instead of an hardcoded DIGEST256_LEN in
order to avoid comparing bytes out-of-bounds with a smaller digest
length such as SHA1. Fixes bug 19066; bugfix on 0.2.2.6-alpha.
o Minor bugfixes (documentation):
- Document the --passphrase-fd option in the tor manpage. Fixes bug
19504; bugfix on 0.2.7.3-rc.
- Fix the description of the --passphrase-fd option in the
tor-gencert manpage. The option is used to pass the number of a
file descriptor to read the passphrase from, not to read the file
descriptor from. Fixes bug 19505; bugfix on 0.2.0.20-alpha.
o Minor bugfixes (ephemeral hidden service):
- When deleting an ephemeral hidden service, close its intro points
even if they are not completely open. Fixes bug 18604; bugfix
on 0.2.7.1-alpha.
o Minor bugfixes (guard selection):
- Use a single entry guard even if the NumEntryGuards consensus
parameter is not provided. Fixes bug 17688; bugfix
on 0.2.5.6-alpha.
- Don't mark guards as unreachable if connection_connect() fails.
That function fails for local reasons, so it shouldn't reveal
anything about the status of the guard. Fixes bug 14334; bugfix
on 0.2.3.10-alpha.
o Minor bugfixes (hidden service client):
- Increase the minimum number of internal circuits we preemptively
build from 2 to 3, so a circuit is available when a client
connects to another onion service. Fixes bug 13239; bugfix
on 0.1.0.1-rc.
o Minor bugfixes (logging):
- When logging a directory ownership mismatch, log the owning
username correctly. Fixes bug 19578; bugfix on 0.2.2.29-beta.
o Minor bugfixes (memory leaks):
- Fix a small, uncommon memory leak that could occur when reading a
truncated ed25519 key file. Fixes bug 18956; bugfix
on 0.2.6.1-alpha.
o Minor bugfixes (testing):
- Allow clients to retry HSDirs much faster in test networks. Fixes
bug 19702; bugfix on 0.2.7.1-alpha. Patch by teor.
- Disable ASAN's detection of segmentation faults while running
test_bt.sh, so that we can make sure that our own backtrace
generation code works. Fixes another aspect of bug 18934; bugfix
on 0.2.5.2-alpha. Patch from "cypherpunks".
- Fix the test-network-all target on out-of-tree builds by using the
correct path to the test driver script. Fixes bug 19421; bugfix
on 0.2.7.3-rc.
o Minor bugfixes (time):
- Improve overflow checks in tv_udiff and tv_mdiff. Fixes bug 19483;
bugfix on all released tor versions.
- When computing the difference between two times in milliseconds,
we now round to the nearest millisecond correctly. Previously, we
could sometimes round in the wrong direction. Fixes bug 19428;
bugfix on 0.2.2.2-alpha.
o Minor bugfixes (user interface):
- Display a more accurate number of suppressed messages in the log
rate-limiter. Previously, there was a potential integer overflow
in the counter. Now, if the number of messages hits a maximum, the
rate-limiter doesn't count any further. Fixes bug 19435; bugfix
on 0.2.4.11-alpha.
- Fix a typo in the passphrase prompt for the ed25519 identity key.
Fixes bug 19503; bugfix on 0.2.7.2-alpha.
o Code simplification and refactoring:
- Remove redundant declarations of the MIN macro. Closes
ticket 18889.
- Rename tor_dup_addr() to tor_addr_to_str_dup() to avoid confusion.
Closes ticket 18462; patch from "icanhasaccount".
- Split the 600-line directory_handle_command_get function into
separate functions for different URL types. Closes ticket 16698.
o Documentation:
- Fix spelling of "--enable-tor2web-mode" in the manpage. Closes
ticket 19153. Patch from "U+039b".
o Removed features:
- Remove support for "GET /tor/bytes.txt" DirPort request, and
"GETINFO dir-usage" controller request, which were only available
via a compile-time option in Tor anyway. Feature was added in
0.2.2.1-alpha. Resolves ticket 19035.
- There is no longer a compile-time option to disable support for
TransPort. (If you don't want TransPort; just don't use it.) Patch
from "U+039b". Closes ticket 19449.
o Testing:
- Run more workqueue tests as part of "make check". These had
previously been implemented, but you needed to know special
command-line options to enable them.
- We now have unit tests for our code to reject zlib "compression
bombs". (Fortunately, the code works fine.)
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